PSYCHOLOGY OF MENTAL DEFICIENCY 



87 



porting at least one field -worker who shall visit the homes whence come defective 

 pupils and determine the mental condition of other individuals of the same germ 

 plasms as are united in the pupil question. The Vineland School has set a 

 shining example of this work and has achieved striking results. These studies 

 really ought to be carried on in every state, not merely to confirm the laws of 

 heredity of imbecility but to determine the main blood lines of imbecility 

 coursing through this country. 



So far we have considered the 

 causes of mental deficiency of he- 

 reditary origin. The causes in 

 general may be grouped roughly 

 under direct, which are due to 

 heredity or disease, and indirect, 

 due to sense defects and accidents. 

 About 85 per cent, of the cases 

 may be traced to conditions prior 

 to birth, such as bad heredity, 

 neurotic conditions, alcoholism and 

 tuberculosis. Injuries at birth 

 are at the present time rare and 

 are responsible for not over 1 per 

 cent., according to the best author- 

 itories. The remainder may prob- 

 ably be counted for by accidents, 



infectious diseases, epilepsy, mal- 



1 . l J Fig. 5. Placing Blocks in the Forji 



nutrition, etc., after birth. Board. With this form board, another 



type of test used in America, the child is 

 required to place the ten blocks as rap- 

 idly as possible in their respective places. 

 The experimenter observes and notes 

 superfluous and jerky movements, the 

 adoption of a method or system, i. e., 

 hunting the block to fit the space and 

 vice versa, the ability to profit by experi- 

 ence when the test is repeated, the ability 

 to increase a set pace of procedure, the 

 degree of sustained attention, the span of 

 motor control, and many other phases of 

 mental expression. One bright boy of ten 

 recently placed the blocks in their re- 

 spective places in twelve seconds and a 

 defective of nineteen required, after much 

 urging and many vacillating and uncoor- 

 dinated movements, seven minutes and 

 eighteen seconds. Dr. Healy, psychopa- 

 thologist for the Chicago Juvenile Court, 

 has modified this type of form board by 

 having the geometric forms a part of a 

 puzzle picture which covers the face of 

 the board. 



This test alone throws much light 

 on the mind of a child and may be used 

 as a diagnostic test for children of vary- 

 ing grades of arrested mental ability. 



Fig. 6. A Test for Reflex Ac- 

 tion and Motor Control. The appa- 

 ratus as shown consists of a piece of 

 glass in a frame which is struck by a 

 rubber hammer. Low-grade defectives 

 seldom wink. 



